A rural farmer believes that his daughter is possessed by a demon in The Last Exorcism, a horror film that, at least in concept, has a clever take on exorcism lore.

And, right off the top let’s just say SPOILER ALERT — if you want total surprise at your viewing of The Last Exorcism, just look for the bolded grade and move on.

Cotton Marcus (Patrick Fabian) is an old-school dyed-in-the-wool preacher who, when he isn’t wowing the crowds at his local church, exorcises demons who plague the faithful.

Sort of.

After the birth of a son with medical problems, Cotton reexamined his career and discovered that his heart wasn’t really in it. He found that he had been more a Bible-thumping entertainer than a holy man and that he didn’t really believe in a lot of what he did, including the exorcisms. Those began to particularly bother him after he read about an exorcism gone wrong where a child died. The movie we’re seeing is a “documentary” that Cotton is making to expose the fakery of exorcisms. He and a crew — a cameraman and Iris (Iris Bahr), the producer — head to a farm in rural Louisiana where Louis (Louis Herthum), a man who wrote to Cotton, believes he is dealing with a demon possession. What Cotton is irritated to learn when he gets out there is that Nell (Ashley Bell), Louis’s teenage daughter, is the one supposedly possessed (Cotton’s whole point is that he wants to prevent more exorcisms on children). Caleb (Caleb Landry Jones), Louis’ teenage son, is initially hostile to the exorcism proceedings but seems OK with it all when he recognizes Cotton’s performing of some sleight of hand that makes water appear to demonically boil when Nell puts her feet in it. My dad’s a superstitious drunk, Caleb says, and it seems like what Cotton has uncovered is not a case of possession but of grief (Louis’ wife died a few years earlier), mental illness and the perils of social isolation.

Or is it?

Most movies about demons and exorcisms start from the place that we need to be convinced to believe, at least enough for the purposes of buying in to the movie. The Last Exorcism cleverly starts from the perspective that it doesn’t believe. It then plays with what we in the audience expect will happen — that we will know the possession is “real” before the characters do — always jerking us away from where we think we’re going. I have to say I liked that. Perhaps it’s a little unfairly meta but I spent most of the movie trying to figure out what the movie was doing, what game it was playing, which way it was trying to go, and I liked that it could keep me guessing. The disappointment is that the movie doesn’t, in the end, do anything with the fun little puzzles it sets up. About 15 minutes before the end, you can feel it all unraveling and it’s disappointing to see that the light touch that went into the beginning is about to be crushed by the end.

But — and perhaps it’s also unfair to judge a movie this way but, hey, we’ve got to work with what they give us — considering how unclever, how very dull-thump-to-the-side-of-the-head most horror movies are, I can almost forgive those last 15 or so minutes. If you like creepy movies at all, see this anyway and enjoy the moments of originality you get. C+

Rated PG-13 for disturbing violent content and terror, some sexual references and thematic material. Directed by Daniel Stamm and written by Huck Botko and Andrew Gurland, The Last Exorcism is an hour and 30 minutes long and is distributed in wide release by Lionsgate.